Engr. Hinesh Kumar
1899 by Prevost
and Batelli, two Italian physiologists .
 They discovered that electric shocks could convert
ventricular fibrillation to sinus rhythm in dogs.
 The first case of a human life saved by
defibrillation was reported by Beck in 1947 .
 Defibrillation was invented in
 Fibrillation
is the rapid, irregular, and
unsynchronized contraction of muscle fibers.
 There are two major classes of cardiac fibrillation:
Atrial Fibrillation and Ventricular Fibrillation.
 Atrial
fibrillation is an irregular and
uncoordinated contraction of the cardiac muscle of
atria.
 Ventricular
Fibrillation is an irregular and
uncoordinated contraction of the cardiac muscle of
ventricles.
Figure:
(a) Normal waveform.
(b) Ventricular fibrillation.
(c) Ventricular tachycardia.
 Defibrillation is a process in
which an electronic device sends
an electric shock to the heart to
stop an extremely rapid,
irregular heartbeat, and restore
the normal heart rhythm.
 Defibrillation should be
performed with in the first 8
minutes after cardiac arrest.
Ideally, the sooner, the better.
 Defibrillator is the device used to
deliver the electrical shock and it can
be manual or automatic.
 Internal Defibrillator
 Electrodes directly placed to the heart
 e.g., ICD (Internal Cardioversion Defibrillator)
 External Defibrillator
 Electrodes placed directly on the chest.
 e.g., AED (Automatic External Defibrillator)
Internal
External
 An
implantable
cardioverter-defibrillator
(often called an ICD) is a device that briefly
passes an electric current through the heart.
 It is "implanted," or put in your body surgically.
 It includes a pulse generator and one or more
leads.
 The pulse generator constantly watches your
heartbeat.
 AED
is a portable electronic device
that
automatically diagnoses the ventricular fibrillation in
a patient.
 Automatic refers to the ability to autonomously
analyse the patient's condition.
 AEDs require self-adhesive electrodes instead of hand
held paddles.
There are two general classes of waveforms:
a) Monophasic waveform
•
Energy delivered in one direction through the
patient’s heart
b) Biphasic waveform
•
Energy delivered in both direction through the
patient’s heart
 A monophasic type, give a high-energy shock, up to 10 to
360 joules due to which increased cardiac injury and in
burns the chest around the shock pad sites.
 A biphasic type, give two sequential lower-energy
shocks of 5 - 200 joules, with each shock moving
in an opposite polarity between the pads.
 Low energy biphasic shocks may be as effective as high
energy monophasic shocks.
 Biphasic waveform defibrillation used in implantable
cardioverter defibrillator (ICD) and automatic external
defibrillators.
1. Lown Waveform
2. Monopulse Waveform
3. Tapered DC Delay
4. Trapezoidal
 In 1962, Dr Bernard Lown of Harward University




introduced the waveform that bears his name.
The voltage and current applied to the patient's chest
plotted against time.
The current will rise very rapidly to about 20 A under
the influence of slightly less than 3 KV.
The waveform then decays back to zero within 5 ms,
and then produces a smaller negative pulse also of
about 5 msec.
The charge delivered to the patient is stored in a
capacitor and is produced by a high-voltage dc power
supply.
Lown Defibrillator Waveform
 The operator can set the charge level using the set
energy knob on the front panel.
 The knob controls the dc voltage produced by the highvoltage power supply and so can set the maximum
charge on the capacitor
 The energy stored in the capacitor is given by:
 where,
 U is the energy in joules (J)
 C is the capacitance of C1, in farads (F)
 V is the voltage across C1, (V)
Calculate the energy stored in a 16-µF capacitor
that is charged to a potential of 5000 V dc.
Solution
 The monopulse waveform shown in figure is a modified
Lown waveform and is commonly found in certain
portable defibrillator.
 This waveform differs from the others in that it uses a
lower amplitude and longer duration to achieve the
energy level.
 The energy transferred is proportional to the area
under the square of the curve, so we may attain the
same energy as in other waveforms.
 The trapezoidal waveform shown in figure is another
low-voltage, long duration shape.
 The initial output potential is about 800 V, which
drops continuously for about 20 ms until it reaches
500 V, where it is terminated .
 Types of defibrillator electrodes:a)
Spoon Shaped Electrode
 Applied directly to the heart.
b)
Paddle type electrode
 Applied against the chest wall
c)
Pad Type Electrode
 Applied directly on chest wall
fig: Electrodes used in defibrillator (a) a spoon shaped internal
electrode that is applied directly to the heart. (b) a paddle type
electrode applied against the anterior chest wall.
Fig.- Pad electrode
 White is negative, anterior chest wall.
Red is Positive , left anterior axillary line.
 “Red on Ribs! White on right!”
• The paddles used in the procedure should not be
placed:• on a woman's breasts
• over an internal pacemaker patients.
• Before the paddle is used, a electrochemical gel must
be applied to the patient's skin to avoid the skin burns.
• Skin burns from the defibrillator paddles are the most
common complication of defibrillation.
• Other risks include injury to the heart muscle,
abnormal heart rhythms, and blood clots.
 Attach the external and internal paddles if the monitor
reads, "No paddles”.
 Check to ensure that the leads are securely attached if
the monitor reads, "No leads.“
 Connect the unit to AC power if the message reads,
"Low battery.“
 Verify that the Energy Select control settings are
correct if the defibrillator does not charge.
 Change the electrodes and make sure that the
electrodes adapter cable is properly connected.
 Close the recorder door and the paper roll if the
monitor message reads, "Check recorder”.